HELP : Stop At Random Frame (charity website)

(my charity work at http://www.huachingfoundation.com)

I only knew a little on ActionScripting but I got a lot of ideas on mind. One of them is random frames. What I thought is this,

on my main movie which I call “interface.swf”, there is movieclip on one timeline that has 6 frames.

The first frame contains this:
gotoAndStop(Math.ceil(Math.random()*4)+1);

Second Frame:
stop();
_parent.bg_container_mc.loadMovie(“swf/randombg01.swf”);

Third Frame:
stop();
_parent.bg_container_mc.loadMovie(“swf/randombg02.swf”);

this goes until the 6th frame which loads
stop();
_parent.bg_container_mc.loadMovie(“swf/randombg06.swf”);

Now my problem is sometimes, it doesn’t load anything, and so I wonder what is going on. I kept on trying, changing the number on the code of the first frame only to get more errors. Thinking that with all that random frame thing, somehow it lands and stops on the first frame. But it’s suppose to do the random again right?

I tried to put this on my first frame just to be sure:
stop();
_parent.bg_container_mc.loadMovie(“swf/randombg01.swf”);

Can anybody please help me with this? Maybe a better script?